Every so often I'll experience what looks like a sudden quick redraw of everything in the content window (the page it self, not the Firefox UI). Sometimes when this occurs the page will look correct but when trying to click on URL's and stuff I'll find that where to click is now misaligned from where the link is visually, same with text boxes and other interactive stuff.

Refreshing the page is the only way to fix the alignment of elements with their visual position when the problem occurs.